Flat Miniature Heat Pipes With Micro Capillary Grooves

Abstract

Flat miniature heat pipes (FMHP’s) are shown to be very promising in the cooling of electronic component systems. This investigation presents a detailed experimental and theoretical analysis on maximum heat transfer capabilities of two copper-water FMHP’s with diagonal trapezoidal micro capillary grooves and one copper-water FMHP with axial rectangular micro capillary grooves. Maximum heat flux on the evaporator wall of the 120-mm long axial grooved heat pipe, with a vapor channel cross-sectional area of approximately 1.5 × 12 mm2 and rectangular grooves of dimensions 0.20 mm wide by 0.42 mm deep, exceeded 90 W/cm2 in the horizontal orientation and 150 W/cm2 in the vertical orientation. Theoretical prediction of the capillary limitation in the horizontal orientation agreed reasonably well with the experimental data.

Heat Pipe for Aerospace Applications—An Overview

“…An overview was presented elsewhere for the development of the micro heat pipe [52]. The fabrication and experimental data on the performance characteristics of the flat water-copper heat pipe with external dimensions 2 × 7 × 120 mm have been reported with radial heat fluxes of 90 W/cm 2 and 150 W/cm 2 for horizontal and vertical applications, respectively [53]. Reference [54] studied the heat transfer limitation of the micro heat pipe and found that the maximum heat-transport capacity of a micro heat pipe depends upon the capillary and fluid continuum limit.…”

Theoretical and Experimental Analysis of Flows and Heat Transfer Within Flat Mini Heat Pipe Including Grooved Capillary Structures

“…It can be seen from this overview that three types of grooved metallic FMHP are developed: i. Type I: FMHPs with only axial rectangular, triangular or trapezoidal grooves (Murakami et al, 1987;Plesh et al, 1991;Sun and Wang, 1994;Ogushi and Yamanaka., 1994;Cao et al, 1997;Hopkins et al, 1999;Schneider et al, 1999aSchneider et al, , 1999bSchneider et al, , 2000Avenas et al, 2001, Cao and Gao, 2002, Lin et al, 2002Chien et al, 2003;Moon et al, 2003Moon et al, , 2004Soo Yong and Joon Hong, 2003;Lin et al, 2004;Romestant et al, 2004;Zhang et al, 2004;Popova et al, 2006;Lefevre et al, 2008;Lim et al, 2008;Tao et al, 2008, Zhang et al, 2009Xiaowu et al, 2009). These FMHPs allow for high heat fluxes for horizontal or thermosyphon positions (up to 150 W/cm²).…”

“…The fabrication of narrow grooves with sharp corner angle is a challenging task for conventional micromachining techniques such as precision mechanical machining. Accordingly, a number of different techniques including high speed dicing and rolling method (Hopkins et al, 1999), Electric-Discharge-Machining (EDM) (Cao et al, 1997;Cao and Gao, 2002;Lin et al, 2002), CNC milling process (Cao and Gao, 2002;Gao and Cao, 2003;Lin et al, 2004;Sarno, 2001, Zaghdoudi et al, 2004;Lefèvre et al, 2008), drawing and extrusion processes (Moon et al, 2003(Moon et al, , 2004Romestant et al, 2004;Xiaowu, 2009), metal forming process (Schneider et al, 1999a(Schneider et al, , 1999b(Schneider et al, , 2000Chien et al, 2003), and flattening (Tao et al, 2008) have been applied to the fabrication of microgrooves.…”

“…Faghri and Khrustalev (1997) studied an enhanced flat miniature heat pipes with capillary grooves for electronics cooling systems, They survey advances in modeling of important steady-state performance characteristics of enhanced and conventional flat miniature axially-grooved heat pipes such as the maximum heat flow rate, thermal resistance of the evaporator, incipience of the nucleate boiling, and the maximum heat flux on the evaporator wall. Khrustalev and Faghri (1999) Launay et al (2004) developed a detailed mathematical model for predicting the heat transport capability and the temperature distribution along the axial direction of a flat miniature heat pipe, filled with water. This steady-state model combines hydrodynamic flow equations with heat transfer equations in both the condensing and evaporating thin films.…”

Analysis of Fluid Flow in Axial Re-entrant Grooves with Application to Heat Pipes

“…The contact angle decreases until the minimum meniscus contact angle φ 0 for the particular solid-liquid combination is reached. Past this point, the meniscus detaches from the top of the groove and recedes into the groove (Hopkins et al [19]). When the meniscus reaches the fillet region of the groove, the cross-sectional area decreases dramatically for small changes in the height of the meniscus attachment point due to the requirement that the contact angle must remain constant, as shown in Fig.…”